Captive screws, or captive panel fasteners are well known in the industry. This type of fastener is arranged so that a screw or a bolt is held in position extending through an opening in a panel, with the threaded end of the screw extending out on the other side of the panel. When large panels with many fasteners are used, for example, in aircraft or similar assemblies, it is important that these fasteners be properly held in position, with the fastener held captive on the panel ready for the securing of the threaded end of the fastener to a nut or into a tapped hole.
One type of captive panel fastener which has been widely used, includes three slots which extend longitudinally from the head through the threaded area of the screw or bolt, adjacent the end of the fastener and which stop short of the end of the fastener. A resilient washer is used with this type of fastener, and after the screw or bolt is extended through a hole in the panel, a flexible washer having three inwardly extending prongs is snapped over the end of the fastener, with a special tool so that the three prongs extend into the three longitudinal slots extending through the threads and the shank of the fastener. The slots must be carefully formed and the outer ends of the slots must be sharply formed, so there is no ramp, which might assist in the flexible washer prongs sliding off the outer end of the fastener. Because the slots must be very accurately formed, they are normally formed by an EDM process in which material is removed by an electrode in a bath. This is a relatively expensive process, and results in a relatively high cost fastener. Even a relatively small fasteners of this type may cost as much as $30.00 apiece for aircraft or missile-type fastener applications.
Incidentally, it may be noted that captive panel fasteners of the type mentioned above in which the retaining washers are secured in slots at the threaded end of the fastener, are advantageous in that the shanks of the screws or bolts between the head and the threads may be of larger outer diameter (OD) and greater strength than many other types of captive panel fasteners, and accordingly carry a full shear load.
An important object of the present invention is to provide a captive panel fastener of the type described hereinabove which is much less costly to produce.